package com.why.blog.common.utils;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;

/**
 * description:
 *
 * @author: taohan
 * @date: 2019年04月11日
 * @time: 10:46
 */
public class DESUtil {

	public static final String DES_KEY = "yc_data_des_key";
	
	private static final String DES = "DES";
	private static final String AES = "AES";

	/**编码格式；默认使用uft-8*/
	private static final String charset = "utf-8";
	/**DES*/
	private static final int keysizeDES = 0;
	/**AES*/
	private static final int keysizeAES = 128;

	/**
	 * 使用DES加密算法进行加密（可逆）
	 * @param res 需要加密的原文
	 * @param key 秘钥
	 * @return
	 */
	public static String DESencode(String res, String key) throws Exception {
		return keyGeneratorES(res, DES, key, keysizeDES, true);
	}

	/**
	 * 对使用DES加密算法的密文进行解密（可逆）
	 * @param res 需要解密的密文
	 * @param key 秘钥
	 * @return
	 *
	 */
	public static String DESdecode(String res, String key) throws Exception {
		if (res == null) {
			return null;
		}
		return keyGeneratorES(res, DES, key, keysizeDES, false);
	}

	/**
	 * 使用KeyGenerator双向加密，DES/AES，注意这里转化为字符串的时候是将2进制转为16进制格式的字符串，不是直接转，因为会出错
	 * @param res 加密的原文
	 * @param algorithm 加密使用的算法名称
	 * @param key  加密的秘钥
	 * @param keysize
	 * @param isEncode
	 * @return
	 */
	private static String keyGeneratorES(String res,String algorithm,String key,int keysize,boolean isEncode) throws Exception {
		try {
			KeyGenerator kg = KeyGenerator.getInstance(algorithm);
			if (keysize == 0) {
				byte[] keyBytes = charset==null?key.getBytes():key.getBytes(charset);
				kg.init(new SecureRandom(keyBytes));
			}else if (key==null) {
				kg.init(keysize);
			}else {
				byte[] keyBytes = charset==null?key.getBytes():key.getBytes(charset);
				kg.init(keysize, new SecureRandom(keyBytes));
			}
			SecretKey sk = kg.generateKey();
			SecretKeySpec sks = new SecretKeySpec(sk.getEncoded(), algorithm);
			Cipher cipher = Cipher.getInstance(algorithm);
			if (isEncode) {
				cipher.init(Cipher.ENCRYPT_MODE, sks);
				byte[] resBytes = charset==null?res.getBytes():res.getBytes(charset);
				return parseByte2HexStr(cipher.doFinal(resBytes));
			}else {
				cipher.init(Cipher.DECRYPT_MODE, sks);
				return new String(cipher.doFinal(parseHexStr2Byte(res)));
			}
		} catch (Exception e) {
			throw new Exception("用户ID异常");
		}
	}

	/**将二进制转换成16进制 */
	public static String parseByte2HexStr(byte buf[]) {
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < buf.length; i++) {
			String hex = Integer.toHexString(buf[i] & 0xFF);
			if (hex.length() == 1) {
				hex = '0' + hex;
			}
			sb.append(hex.toUpperCase());
		}
		return sb.toString();
	}

	/**将16进制转换为二进制*/
	public static byte[] parseHexStr2Byte(String hexStr) {
		if (hexStr.length() < 1)
			return null;
		byte[] result = new byte[hexStr.length()/2];
		for (int i = 0;i< hexStr.length()/2; i++) {
			int high = Integer.parseInt(hexStr.substring(i*2, i*2+1), 16);
			int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);
			result[i] = (byte) (high * 16 + low);
		}
		return result;
	}

	public static void main(String[] args) {
		//String deSencode = DESencode("da808cee62774a479818c501e45ec6dc", DES_KEY);
		//System.out.println(deSencode);

		try {
			System.out.println(DESdecode("1212GDFGS", DES_KEY));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}
